Swim-trained rats have greater bone mass, density, strength, and dynamics.

Weight-bearing exercise is traditionally recommended for improving bone health in postmenopausal women. Effects of swim exercise were studied as an alternative to weight-bearing exercise in ovariectomized rats. Rats in a swim group (Sw, n = 8) swam for 12 wk, 5 days/wk for 60 min per session. A control group (Con, n = 9) engaged in no structured exercise. Femurs were analyzed for bone mineral density and for bone mineral content by dual energy X-ray absorptiometry, biomechanical properties by three-point bending (Instron), and bone structure and formation by histomorphometry. Food intake did not differ among groups. Final body weights were significantly lower in Sw compared with Con (P < 0.05). Swimmers had significantly greater femoral shaft bone mineral density and content (P < 0.05) compared with Con. Femurs of the Sw group had greater mechanical properties (P < 0.05) compared with Con. Histomorphometric data were significantly better in the Sw group compared with Con after the 12-wk intervention (P < 0.05). In conclusion, data from this study demonstrate some beneficial effects of swim exercise on bone structure, turnover, and strength.